The present invention relates to a device for use in moving a load up or down a stepped path such as a staircase. It is particularly, though by no means exclusively, applicable to invalid chairs.
According to one aspect of the present invention there is provided a device for use in moving a load up or down a stepped path, comprising a structure for receiving the load, at least one support element rotatably mounted on the structure and having rotatably mounted thereon at least three symmetrically disposed wheels whereby, in use, the wheels cooperate with successive steps of the path, and foot means secured to each support element adjacent the corresponding wheel, the foot means being clear of the circumference of the wheel at two regions so that the wheel can roll freely on a plane when the support element is positioned with the wheel and respectively one or other of the adjacent wheels in contact with the plane, and having engagement portions located forwardly of the said two regions so as, when the support element is rotated forwardly of the said position, to engage the plane to prevent rolling movement.
Normally the clear regions will be disposed symmetrically on each side of a radius of the support member passing through the axis of the wheel in question; one engagement portion being on this radius and the other lying forwardly of the forwardmost of the two clear regions. "Forward" is with reference to the direction downwardly of the stepped path: where the device has a handle, usually the device will move up the path handle-first. If the device does not have a preferred direction, then naturally three engagement portions should be provided, respectively rearwardly, between, and forwardly of the two clear regions. Indeed, it may sometimes be convenient to provide three engagement portions even in devices having a preferred direction.
In one preferred arrangement, the foot means takes the form of a further wheel, non-rotatably mounted on the support member, coaxial with, said having a diameter equal to or slightly greater than, the rotatable wheel, the cutaway portions corresponding to the "clear" regions and circumferential or rim portions forming the said engagement portions.
In another aspect, the invention provides a device for use in moving a load up or down a stepped path, comprising a structure for receiving the load, at least one support element rotatably mounted on the structure and having rotatably mounted thereon at least three symmetrically disposed wheels whereby, in use, the wheels cooperated with successive steps of the path, and a rotatable member connected to the support element(s) by gearing means such that, in use the rotatable member rotates at a greater speed than the support element(s), whereby during movement down the stepped path, drag on the rotatable member provides, with a mechanical advantage, a restraining effect on rotation of the support elements.
The drag on the rotatable member may be provided by motor winding resistance and friction: indeed the member may simply be the rotor of a motor employed for driving the support member(s) during movement up the stepped path, or by brake drum or disc (which could be mounted on a common shaft with such a motor, or both). The motor braking can be enhanced by an electrically operated dynamic motor braking arrangement.
In a further aspect the invention provides a device for use in moving a load up or down a stepped path, comprising a structure for receiving the load, at least one support element rotatably mounted on the structure and having rotatably mounted thereon at least three symmetrically disposed wheels whereby, in use, the wheels cooperate with successive steps of the path, and a motor arranged to drive the support element(s), the motor being pivotally mounted about an axis substantially coincident with that of the support element(s), and an elongate forwardly extending stabilizing element secured for pivotal movement together with the motor so as, in use, to bear on the stepped path.
Although it is possible to employ only one support element, for many applications this will create problems of balance, and the use of two support elements is preferred. More than two may be provided, but this will not usually be necessary.
Preferably the or each support element is a "spider" having radially extending symmetrical arms each carrying a respective wheel. Four wheels are preferred.
Where there are two support elements, these may be rigidly secured to a common axle which is rotatably secured to the structure.
Preferably also the structure includes a handle for the person moving the load, for steering and guiding the load.
As previously mentioned, the invention may be applied to invalid chairs, and thus also provides a device of the type described above including a seat for receiving a patient.